1. Field of the Invention
The present invention relates to freehand writing instruments, and in particular, to instruments that are motorized to alter the writing.
2. Description of Related Art
For a freehand writing instrument to maintain a comfortable feel, the angular orientation of the writing tip should be parallel or close to parallel to the centerline or longitudinal axis of the instrument. The tolerable amount of angular displacement from parallel depends on whether the writing tip lies on the centerline (longitudinal axis) of the writing instrument, or whether the writing tip is offset from this centerline (asymmetrical placement). For an asymmetrically placed writing tip, greater angular displacement of the writing tip is tolerable since the asymmetrical offset itself creates an inherent angular offset that can be compensated somewhat by tilting the writing tip. The tolerable angular displacement of the writing tip is a function of the inherent angle between the centerline (longitudinal axis) of the writing instrument and a line originating on the instrument""s centerline at the upper (distal) end of the writing instrument and running to the lower (proximal) end of the instrument, terminating at a distance from the centerline representing the asymmetrical offset of the writing tip from this centerline. In effect, asymmetrical writing instruments having a greater asymmetrical offset can tolerate a writing tip with a greater tilting from an orientation parallel to this centerline (longitudinal axis) of the writing instrument.
Writing instruments have been designed to alter the appearance of a writer""s normal strokes. Such devices have been designed purely for entertainment or to produce special effects needed for specialized drawings.
In U.S. Pat. No. 3,997,972 a writing instrument 17 is connected to a spinning shaft 11a by a flexible coupler 18. In the examples of FIGS. 2 and 3, special effects are produced by pressing the spinning tip of the writing instrument 17 so it rolls or xe2x80x9cwalksxe2x80x9d back and forth across the writing surface (parallel strokes of FIGS. 7 and 12). Alternatively, the writing instrument can be held upright as shown in FIG. 4 so that the tip of the writing instrument can roll along a somewhat erratic spiral path, as shown in FIGS. 8-11. In any event, the speed of the writing tip is disadvantageously determined by the rolling properties of the tip. Also, xe2x80x9cwalkingxe2x80x9d the spinning writing tip in this way quickly wears the tip.
For the embodiments of FIGS. 5 and 6 of U.S. Pat. No. 3,997,972, the writing tip follows a conical orbit, staying essentially aligned as a conical ray (subject to some skewing due to flexing of coupler 18). (FIG. 6 may be deemed a cone with a zero conical angle.) When the barrel is tilted in a natural way as shown, the writing pressure varies orbitally. A problem with this design is that the angle of the writing tip 17 is quite different from the angle of the barrel 10. Consequently, the feel of the writing tip is changed by the canting of the tip 17 relative to the barrel 10. If however, the angle between the writing tip 17 and barrel 10 were to be kept small, the amplitude of oscillations of the tip will remain too small.
In U.S. Pat. No. 5,752,870 a toy moves along a surface to drive a wheel, while pens are thereby rotated to draw a pattern on the surface. The pens are held in a turret 57 (FIG. 6) and rotate about a shaft 51. This arrangement requires the wheels and other rollers to remain on the writing surface, so that the assembly maintains a constant parallel orientation to the writing surface. Thus, this device cannot be used like a simple freehand writing instrument. This apparatus lacks a free expressive quality, and must be moved about with a limited motion, much like a scrub brush. See also U.S. Pat. No. 3,638,319 for a wheel-driven toy where the writing instruments are held on the toy, but not mechanically rotated.
In U.S. Pat. No. 4,835,874 a marking device attached to a ring gear can orbit inside a handheld device as it slides across a drawing surface. This assembly must remain flat on the writing surface and is pushed around that surface with a scrubbing motion. Thus, this reference does not allow the expressive strokes possible with a freehand writing instrument.
In U.S. Pat. Nos. 3,390,460; 5,208,987; and 5,433,642 an eccentric weight is spun in the upper end of a writing instrument to cause oscillations about the writer""s fingers. These spinning mechanisms must generate substantial force to overcome the writer""s grip. Consequently, a substantial mass must be placed at the end of the writing instrument, which will tend to produce an off-balanced feel. Also, since the vibrations must necessarily be transferred through the writer""s fingertips, this device will quickly become uncomfortable and have a tendency to numb the writer""s fingertips.
In accordance with the illustrative embodiments demonstrating features and advantages of the present invention, there is provided a freehand writing instrument for holding a writing tip. The instrument is operable to draw the writing tip across a writing surface in one or more strokes. The instrument has a case sized to be handheld and has a longitudinal axis extending between a distal and proximal end of the case. Also included is a motor mounted at the case. The writing instrument also has an element mounted at the proximal end of the case. The element is driven by the motor to move periodically about a predetermined center reaching a maximum transverse displacement from the center. With the distal end of the case defined as a vertex, this maximum transverse displacement is sized to subtend a displacement angle with respect to the longitudinal axis. The element has a holder adapted to transversely hold the writing tip at an orientation displaced from parallel to the longitudinal axis no more than the displacement angle. The element is operable to produce a periodic pattern on the writing surface during the strokes. The element has clearance to permit the writing tip to write with the case held at varying angles of inclination within a range of angles relative to the writing surface. The angle of inclination is adjustable to alter the periodic pattern.
By employing apparatus of the foregoing type, an improved writing instrument is achieved. In a preferred embodiment a cylindrical case contains a battery and a motor driven by the battery. A motor-driven shaft extending from the case supports a claw-like arm that is connected, preferably, at right angles to the motor shaft. A pen, pencil or other writing tip can be held in the arm substantially parallel to the shaft and the longitudinal axis of the case. This orientation gives the writing instrument an overall proper feel.
By pressing a pushbutton on the case the motor can spin the arm, preferably, in a plane perpendicular to the motor shaft. Depending upon the angle of inclination of the writing instrument, the writing tip can write connected loops or successive disconnected marks. In some embodiments the writing tip may be allowed to wobble slightly in which case the writing pattern can be more complex and somewhat chaotic or random.